Overview

Hypocholesterolemia is the presence of abnormally low (hypo-) levels of cholesterol in the blood (-emia). Low cholesterol levels can be defined as a total cholesterol and LDL-C levels inferior to the 5th percentile of the general population adjusted for age, gender and race.[1] The cut-off point used to define hypocholetsterolemia lies between 120 mg/dl and 150m/dl.

Natural History, Complications, and Prognosis

With the increased use of medication to suppress cholesterol, some have expressed concern that lowering cholesterol levels excessively will itself cause disease. While hypercholesterolemia, the presence of high cholesterol, has been linked strongly with cardiovascular disease, it is much less certain whether low cholesterol levels are intrinsically harmful.

Specific disease entities

Demographic studies suggest that cholesterol levels form an U-shape curve when plotted against mortality; this suggests that low cholesterol is associated with increased mortality, mainly due to depression, cancer, hemorrhagic stroke and respiratory diseases[4]. It is possible that whatever causes the low cholesterol level also causes mortality, and that the low cholesterol is simply a marker of poor health[5].

Links with depression have been supported by studies[6]. In contrast, no evidence was found for a link with hemorrhagic stroke (although higher cholesterol levels conferred a relative protection), and neither did statin drugs worsen the risk[7].

The Heart Protection Study found no increase in either respiratory disease or neuropsychiatric illness in a large trial population taking a statin drug[8].

Elderly

In the elderly, low cholesterol may confer a health risk that may not be offset by the beneficial effects of cholesterol lowering[9]. Similarly, for elderly patients admitted to hospital, low cholesterol may predict short-term mortality[10]

Critical illness

Low cholesterol levels are predictive of clinical deterioration, and are correlated with altered cytokine levels[11].

Low cholesterol might be a prognostic sign in hospitalized patients.[12][3]